OK, just a follow-up for posterity. I could not bring myself to use either of the repo commission plates. The original has raised lettering, whereas the repos are painted on an absolute flat plate. The repo's also have different info...the worst of which was trying to add 50 kilos to my trim lady!
So, here is the process I went through. The first problem as that the PO had painted right over the plate, so the gold had to come off.
I did this in a galss bead cabinet. The blasting curls the thin metal, so I had to heat it afterwards with a torch to anneal it and allow it to settle into it's "flat" shape. This has to be done very carefully, as it is just thin aluminum. An oven on 500 degrees would accomplish the same thing, although it would take longer. (I'm impatient!)
As you can see, I was not concerned with a small amount of the original black paint. I just needed to remove the gold. At this point I taped the edges and the raised portion with the vehicle number.
The plate was then painted with a good quality spray-can enamel black paint. Once it dried, I removed the tape and carefully sanded the lettering with 400 grit to bring the letters back out. (note: I tried the finer grits, but I was way too impatient, again!) Once I was happy with the look, I sprayed the entire plate with clear laquer to bring the shine back out of the black paint.
And the final mounting was done with standard Monel pop rivets. The only tricky thing here is that the original plate had the center of the rivet cut cleanly flush with the outer surface of the rivet. If you just pop a modern one in, it will break the center well inside the rivet. So, I pulled the rivet until it was snug, and then used a dremel to cut the center flush...just like the original. I also used sealant on the rivet and back of the plate to keep any stray water out of the passenger footwell.
So, it was well worth saving the original plate.
John